Starting in 2019, 15 state parks will join Colorado’s “reservation only” group, to which five parks already belong. Under the system, campers can reserve a site 24 hours a day, seven days a week. Reservations are available six months in advance up until the day of arrival, according to Colorado Parks and Wildlife. Reservations can be made by logging into cpwshop.com or by calling 800-244-5613. Parks joining the program Jan.